The closures shut down entire commercial districts and emptied out typically buzzing business corridors. It was an unprecedented move, but Friday was an unparalleled day.

Kendall Square in Cambridge, one of the nation’s leading technology hubs, was especially quiet. Streets that would have teemed with tech workers and students on a pleasant spring day were vacant. Sidewalks were clear, coffee shops empty, and complete office blocks seemingly uninhabited.

“It’s a ghost town. It’s kind of scary,” said Jimmy Carbone, a Cambridge taxi driver whose cab idled in front of the Marriott Hotel near the Massachusetts Institute of Technology, waiting for fares that had vanished.

The area is near the scene of the Thursday night fatal shooting of an MIT police officer, allegedly by bombing suspects Dzhokhar A. Tsarnaev and his brother, Tamerlan Tsarnaev. The incident set off a frantic hunt for the men, and early Friday morning Tamerlan was killed in a firefight with police.

Security officers stood outside office buildings around Kendall Square Friday, but pedestrians were rare. The occasional Massachusetts Institute of Technology student hurried to a lab, despite the school’s advice they should stay home, and indoors.

“It’s hard to keep a grad student away from the lab,” said Lucas Willemsen, who is one of those students.

But the vast majority of people did not venture out to work or do anything else.

Tiny two-person Internet start-ups along with the big tech companies based in the neighborhood were closed. The Cambridge Innovation Center, home to more than 500 small companies, along with firms such as HubSpot Inc., Microsoft Corp., and Biogen Idec Inc. were all mostly quiet.

The few employees in offices were the most critical workers. For example, at the Biogen Idec production plant in Cambridge, where the company works around the clock to make a drug to treat multiple sclerosis, there was a small contingent of manufacturing employees to oversee crucial operations.

“Anybody who was not involved in manufacturing was told not to come in, but you have to keep running the plant all the time,” said Dan McIntyre, senior vice president of Biogen Idec.

Meanwhile, many of the biotechnology company’s employees worked remotely from home.

That was also true at other area businesses, as housebound workers connected via laptops and teleconferences. The Cambridge software company HubSpot set up virtual chat rooms for its employees, and drug maker Vertex Pharmaceuticals Inc. kept going with employees logging in on the Internet.

“There’s conference calls taking place that would have been meetings in the office,” said Vertex spokesman Zachry Barber.

Across the river in Boston, the scenes along sidewalks and in offices were similarly ghostly.

“It’s like ‘Planet of the Apes’ down here,” Michael Vaughan said about the streets around his South Boston public relations office. “The town is just dead.”

The benches that line a Duck Boat waiting area on Huntington Avenue were occupied by a lone homeless woman who was sleeping.

Equity Office Properties, the region’s largest commercial landlord, closed nearly all 20 of its office buildings around Boston and Cambridge, including massive complexes such as Center Plaza and One Post Office Square in Boston, and One Memorial Drive in Cambridge.

Its buildings were desolate, save for scattered early risers who got in before authorities instructed people to stay home. Equity Office told anyone who arrived at its buildings to stay inside until the manhunt was over.

“Most people take the T, and since they shut that down, nobody is coming in,” said Larry DiCara, a lawyer for the Boston firm Nixon Peabody. “I hope they get the guy, and I hope it happens soon.”

But not everything stopped Friday in Boston. Some cafes remained open, many Dunkin’ Donuts were still serving coffee, and some tourists were out and about.

“I’m just trying to find somewhere to go,” said Robbin Huntsberger, who came to Boston from Tallahassee, Fla., with her husband, who was in town on business.

Several conferences did take place as scheduled. The Ambulatory Surgery Center Association’s annual meeting, which began Wednesday, continued at the Hynes Veterans Memorial Convention Center, although the Massachusetts Convention Center Authority urged attendees who were not already at the center as of early afternoon not to attempt to travel to the Hynes until further notice.

Attendees who did show up were greeted with a “vigorous security screening,” according to James Rooney, executive director of the convention authority.

Boston Comic Con postponed its comic book convention scheduled for Saturday and Sunday at the Hynes Veterans Convention Center, citing the lock-down, which was lifted late Friday afternoon.

People outside of Boston who needed to conduct business with companies based here seemed to understand why work had been put on hold.

“Most of the clients from out of town are very empathetic,” said Robert Griffin, a managing partner at the real estate firm Cushman & Wakefield. “A lot of them are just saying, ‘Hey, let’s just work on this Monday or Tuesday.’ ”

Michael B. Farrell can be reached at michael.farrell@globe.com. Robert Weisman and Katie Johnston of the Globe staff contributed to this report.

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